<?php 
$username = $_POST['username'];
$password = $_POST['password'];
if($username==''||$password==''){
	echo "<script>window.history.back();alert('用户名或密码不能为空！');</script>";
	exit();
		
}
//echo '用户名:'.$_POST['username'];
//echo '密码:'.$_POST['password'];
 ?>